1. Field of the Invention
The present invention relates to an operation control technique for improving the ride comfort of an escalator, and in particular, to an operation control apparatus for an escalator which is capable of suppressing running vibration due to a footplate by using a vibration-damping control compensator.
In the escalator, an automatic operation means an operation mode for stopping an operation when no passenger intending to use the escalator, in order to save energy and broaden the product""s life time. For this, there is provided a detection device for detecting the entrance and passage of a passenger. When the entrance of a passenger is detected, the escalator is operated at a constant acceleration, and then when a passenger reaches the point of entrance to a step, the escalator is operated at a nominal speed thereafter. With the lapse of certain amount of time since the last passenger""s passing by the escalator, the operation of the escalator is stopped.
In order to perform the above automatic operation, an inverter having a power rectifier is usually employed. In addition, a power transmission device for the movement of the footplate of the escalator is constructed in such a way that a machine shaft having an induction motor and a gear is connected with a shaft of a sprocket having a terminal gear by a chain, to thereby rotate the sprocket. That is, a groove of semi-circumferential shape is formed at the circumferential portion of the sprocket, which is rotated, being engaged with a roller connected to a lower portion of the footplate. When they are engaged with each other, imbalance of torque occurs to thereby generate vibration, which vibration is transmitted to the footplate, thus decreasing the ride comfort.
The present invention is intended to remove electric components sensed on the footplate by detecting a position at which the roller and the sprocket are engaged using a position sensor attached on the shaft of the sprocket, inputting a detection signal thereof to the control apparatus, extracting a pulse component of the torque by a speed detector installed at the shaft of the induction motor, and then applying a torque whose magnitude and phase are opposite to the above torque to the induction motor.
2. Description of the Background Art
FIG. 1 is a block diagram of an operation control apparatus for an escalator in accordance with the conventional art. As illustrated therein, an operation control apparatus for the escalator includes: a power rectifier 2 for converting a three-phase AC utility power into an AC power of variable voltage and variable frequency in order to control the operation speed of the escalator; an induction motor 3 which is driven by output power of the power rectifier; a gear 4 and a sprocket for running a footplate using rotatory force generated from the induction motor 3; a current detector 6 for detecting a current flowing in the induction motor 3; an electromagnetic contactor 7 for transmitting the utility power to the power rectifier 2 in an operation mode and interrupting the same in a non-operation mode; a display device 8 for displaying a running condition and failure of the escalator; a passenger detecting device 9 for detecting an access of a passenger intending to use the escalator; and a control device 10 for appropriately controlling the driving of the induction motor 3 by the power rectifier 2, for thereby operating the escalator at a target speed.
The control device 10 includes: a CPU 11 for performing an operation for driving the induction motor 3 at a variable voltage and variable frequency according to a program stored in a ROM 12; a RAM 13 in which data needed in the CPU 11 is stored; an input device 14 for a signal inputted from the current detector 6, the passenger detecting device 9 and a rotational speed detector 20 into an appropriate form; an output device 15 for driving the display device 8 and the electromagnetic contactor 7 under the control of the CPU 11; a failure detection device 16 for detecting a failure on the basis of an output signal of the input device 14 and an operation pattern setting device 17 for setting a subsequent operation pattern; a pulse width modulation signal generator 18 for generating a pulse width modulation signal according to a signal of the CPU 11 in order to generate an AC power of target form from the power rectifier 2. The operation of the control device 10 will be explained in detail with reference to FIGS. 2 and 5.
When a passenger intending to use the escalator approaches to the entry of the escalator in a state in which the operation of the escalator is stopped, the approach is detected by the passenger detection device 9 and a signal thereof is inputted into the input device 14 of the control device 10. At this time, the CPU 11 performs the operation for driving the induction motor 3 at a variable voltage and variable frequency and operates the electromagnetic contactor 7 according to the program stored in the ROM 12. According to this, an a contact switch 7A of the electromagnetic contactor 7 is short-circuited and thus the three-phase AC utility power 1 is inputted into the power rectifier 2. In addition, the pulse width modulation signal generator 18 generates a pulse width modulation signal corresponding to the operation result of the CPU 11, and accordingly the power rectifier 2 converts the three-phase AC utility power 1 supplied by the a contact switch 7A into a DC voltage and then generates an AC of variable voltage and variable frequency in order to control the torque corresponding to the target speed and load of the induction motor 3, whereby the induction motor 3 is rotated at the corresponding speed. The rotatory force of the induction motor 3 is transmitted to the sprocket 5 through the gear 4 and the chain, and thus the groove positioned on the circumference of the sprocket 5 and the step roller of the footplate are engaged to thereby be rotated. By this, the passenger can move up to a target story using the escalator.
Thereafter, when the absence of a passenger is detected by the passenger detecting device 9, the CPU 11 slows down the escalator according to the automatic operation program stored in the ROM 12 to thus stop it. According to circumstances, a low speed idle operation is performed without stopping the escalator in order to prevent a failure confusion phenomenon. In this state, when the presence of a passenger is detected by the passenger detecting device 9, the escalator is operated at a normal speed by the above process.
Meanwhile, FIG. 3 is a functional block diagram illustrating the inverter control process of the power rectifier 2 in order for the CPU 11 of the control device 10 to control the rotational speed of the induction motor according to the program stored in the ROM 12. The difference between a speed command value Wr* of a speed command unit 11A and an actually detected speed value Wr is obtained by a substractor 11B and then is inputted to a speed controller 11C, and the difference between an output current I* of the speed controller 11C and an actual current value I of the induction motor 3 detected by the current detector 6 is obtained by a substractor 11D and then is inputted to a current controller 11E. Herein, the inverter of the power rectifier 2 is driven by the output value amplified by a predetermined operational process, and thus an induction motor 11F is rotated at a predetermined speed Nr.
FIG. 4 is a signal flow chart illustrating the inverter control process of the power rectifier in accordance with the conventional art, which will be described in detail as follows.
First, it is determined whether or not there is an inverter operation command in S1. If there is an operation command, it is determined whether or not t is a speed control period in S2. If so, a motor speed value Wr is inputted in S3, a speed controller is operated in S4, and then it is determined whether or not t is a current control period in S5. Meanwhile, if there is no operation command in S1, the routine is terminated. In addition, if t is not a current control period in S4, the routine returns to S5. It is determined whether or not t is a current control period in S5. If not, the routine returns to S1, or if so, a motor current value I is inputted in S6, the current controller is operated in S7, and then the inverter is driven by generating a pulse width modulation signal in S8.
FIG. 5 illustrates a rotation frequency of the sprocket 5 containing a harmonic wave of a pulse component by means of a connecting structure for driving the footplate of the escalator. The harmonic wave of the pulse component is occurs due to the imbalance of the torque generated when the step roller and the groove of the sprocket 5 are engaged to thus be rotated. An analysis thereof using a frequency spectrum is illustrated in FIG. 6.
Namely, if the surface of the sprocket 5 which is interlocked with an upper terminal gear engaged with the induction motor 3 to thus be rotated is positioned at the top, the amplitude is generated at the maximum plus (+) value. If a mountain-shaped portion is positioned at the top by further rotation at a predetermined angle, vibration having the maximum minus (xe2x88x92) value is generated periodically.
Due to the above imbalance of the torque generated when the step roller and the groove of the sprocket 5 are engaged to thus be rotated, a pulse component is also found at the footplate speed of the escalator.
FIG. 7 illustrates the footplate speed of the escalator. The pulse frequency of the footplate speed is determined according to the period during which the step roller is engaged with the groove of the sprocket 5.
In the escalator in accordance with the conventional art, there is a disadvantage that vibration due to the imbalance of the torque is generated when the step roller and the groove of the sprocket are engaged to be thus rotated, which vibration is transmitted to the footplate, thereby degrading the ride comfort.
Accordingly, it is an object of the present invention to provide an operation control apparatus for an escalator which is capable of outputting a vibration torque compensating current and removing a torque pulse generated at a footplate by using a detector for detecting a pulse rate generated at a sprocket and a device for detecting the magnitude of a pulse torque of an induction motor without changing the circumferential shape of the sprocket and the connecting structure of the footplate.
To achieve the above object, there is provided an operation control apparatus for an escalator in accordance with the present invention which includes: a power rectifier 2 for converting a three-phase AC utility power into an AC power of variable voltage and variable frequency in order to control the operation speed of the escalator; an induction motor 3 which is driven by output power of the power rectifier; a gear 4 and a sprocket for running a footplate using rotatory force generated from the induction motor 3; a current detector 6 for detecting a current flowing in the induction motor 3; an electromagnetic contactor 7 for transmitting the utility power to the power rectifier 2 in an operation mode and interrupting the same in a non-operation mode; a display device 8 for displaying a running condition and failure of the escalator; a passenger detecting device 9 for detecting an access of a passenger intending to use the escalator; a speed detector 21A for detecting the rotational speed of the induction motor 3; a position detection 21B for detecting the rotational position of the sprocket 5; and a control device 60 which drives the power rectifier 2 by obtaining a vibration torque compensating current from an output signal of the speed detector 21A and the position detector 21B, adding the above current to an output current of a speed controller, subtracting an actual current detection value of the induction motor 3 from the resultant current value, and accordingly generating a pulse width modulation signal.